1. Field of the Invention
This invention relates to a semiconductor inspection apparatus for inspecting functions and the like of surface-mount type semiconductor devices.
2. DESCRIPTION OF THE RELATED ART
FIG. 22 is a perspective view of an external appearance of a semiconductor inspection system 200 having a semiconductor inspection apparatus. The semiconductor system 200, called a handler, is arranged to perform function tests, such as a screening test and a burn-in test. The semiconductor inspection system 200 includes a supply unit 210 in which untasted semiconductor devices are accommodated, a measuring unit 220 for performing inspection, a storage unit 230 for accommodating inspected semiconductor devices. In the measuring unit 220, a chamber capable of changing the temperature and other conditions of an inspection atmosphere is formed. Therefore, these units are partitioned with walls (not shown), and only their portions through which semiconductor devices are transported are connected to each other.
FIG. 23 schematically shows the internal construction of the semiconductor inspection system 200 for explanation of the procedure of transporting semiconductor devices. When semiconductor devices are inspected, they are handled as units each consisting of a plurality of semiconductor devices mounted on pallets. The supply unit 210 contains unmeasured pallets 212 on which uninspected semiconductor devices are mounted, and unloaded pallets 213. Ordinarily, a group of 20 to 30 pallets laid on each other is input to the supply unit 210 through an openable portion 211 (see FIG. 22) on the front side at one time. Unloaded pallets are successively moved to an inner position for unloaded pallets 213. Each semiconductor device is moved from the position on the pallet 212 to one of catchers of a rotary transport mechanism 214 in an aerial transport manner, and is transported to the vicinity of a preliminary heating unit 221 of the inspection unit 220 by a rotary motion of the rotary transport mechanism 214.
The semiconductor device is then moved in an aerial transport manner to a catcher of the preliminary heating ring 221 in a position indicated at 221a. The preliminary heating ring 221 ordinarily has about twelve catchers on which semiconductor devices are mounted. The semiconductor device mounted at the position 221a a undergoes preliminary heating for inspection while the ring 221 makes one revolution. The semiconductor device heated and returned to the position 221a is moved to a central socket frame 20 shown in FIG. 24 in an aerial transport manner.
Next, the Semiconductor device on the socket frame 20 is inspected while its leads are pressed against contact terminals located below the leads by a movable pressing device 30 shown in FIG. 24. After being inspected, the semiconductor device is moved to a recovery table 232 from the socket frame 20 in an aerial transport manner. According to the result of inspection, in the storage unit 230, the semiconductor device is moved in an aerial transport manner onto a defective storage pallet 233 if it is defective or onto a non-defective storage pallet 234 if it is non-defective. Unloaded pallets 235 are successively moved to and superposed on non-defective storage pallets 234 as the non-defective storage pallets 234 are fully loaded. When a certain number of pallets 233 and 234 on which inspected semiconductor devices are mounted are collected, they are taken out through the openable portion 231 (see FIG. 22) of the storage unit 230.
The aerial transport in the above-described transport process is performed with an aerial transport mechanism (not shown) which takes up each semiconductor device by, for example, vacuum to transport the semiconductor device. Each of the supply unit 210, the measuring unit 220 and the storage unit 230 has several aerial transport mechanisms. Each of the supply unit 210 and the storage unit 230 further has a lift mechanism (not shown) for gradually moving superposed pallets in a vertical direction.
FIG. 24 is a perspective view of a conventional semiconductor inspection apparatus 1 which is provided in the measuring unit 220 shown in FIG. 23, and with which inspection of semiconductor devices is practiced. The semiconductor inspection apparatus 1 is formed of the socket frame 20 and the movable pressing device 30. The socket frame 20 is fixed on, for example, a board-like member (not shown), while the movable pressing device 30 is connected to, for example, an actuator such as a cylinder or motor (not shown) and is movable in a vertical direction on the socket frame 20. A semiconductor device 100, i.e., a tested article, has a package 101 in which a semiconductor chip (not shown) is embedded and a plurality of external leads 102 extending out of the package 101. The leads 102 have mounted surfaces which are brought into contact with electrode pads on a printed circuit board or the like (not shown) when the semiconductor device 700 is mounted on the printed circuit board. On the socket frame 20 are provided contact terminals 40 arranged with the same pitch as the external leads 102 of the semiconductor device 100. The socket frame 20 has guides 21 for positioning the package 101 of the semiconductor device 100 so that the external leads 102 correctly contact the corresponding contact terminals 40. The guides 21 are provided on four corner portions of the socket frame 20. The contact terminals 40 are illustrated in FIG. 24 as if they are exposed, although they are actually provided in guide grooves 22 shown in FIGS. 25 and 26. The movable pressing device 30 has a lead pressing potion 31 with which the external leads 102 of the semiconductor device 100 mounted on the socket frame are pressed against the contact terminals 40, a block 32 to which the lead pressing portion 31 is attached, and a drive shaft connected to a cylinder or the like for moving the movable pressing device 30 in a vertical direction. In a state where the semiconductor device 100 is placed on the socket frame 20 and where the external leads 702 are pressed against the contact terminals 40 by the movable pressing device 30, inspection tests of the semiconductor device, i.e., a screening test, a burn-in test and the like, are performed.
FIG. 25 is a cross-sectional view showing a state of inspection in which the semiconductor device 100 is placed on the socket frame 20 and the external leads 102 are pressed against the contact terminals 40 by the pressing device 30. FIG. 26 is an enlarged partially fragmentary perspective view showing a state in which the external leads 102 of the semiconductor device 100 and the connection terminals 40 contact each other. Each of the contact terminals 40 provided on the socket frame 20 has a contact portion 41 which contacts the corresponding one of the external leads 102, a curved portion 42 which enables the contact portion 41 to elastically contact the external leads with a suitable contact pressure, and an electrode portion 43 connected to an external inspection measurement circuit (not shown), and a contact surface 44 (see FIG. 25) which contacts the mounted surface 104 of the external lead 102. As illustrated, the contact terminals 40 are set in the guide grooves 22 that position and guide the contact terminals 40. In FIG. 26, an outer portion of the socket frame 20 is cut way to show the relationship between the guide grooves 22 and the contact terminals 40.
The operation of the inspection apparatus will be described below. Electrical characteristics of semiconductor devices 100 to be tested are measured under a temperature condition of -50.degree. to +125.degree. C. in the chamber of the measuring unit 220 shown in FIG. 22 while being maintained in the state shown in FIG. 25.
The external leads 102 arranged to have their mounted surfaces 104 brought into contact with the contact surfaces 44 of the contact terminals 40 which are formed of a metal and which are elastic and good conductors are pressed by the lead pressing portion 31 of the pressing device 30 with a predetermined pressure. Each contact terminal 40 is formed of a metal, e.g., beryllium copper or phosphor bronze. The pressing device 30 is formed of a heat resistant insulating material such as quartz, sapphire, polyimideamide, MC nylon, polyether sulfone or the like. The predetermined pressure with which the external leads 102 are pressed is at least greater than a value obtained by multiplying the elastic force by the number of contact terminals 40. Pressing is performed with an actuator (not shown) such as a cylinder or a motor attached to the drive shaft 33. By this pressing and by virtue of the elasticity of the curved portions 42 of the contact terminals 40, a reaction against the pressure downwardly applied is caused and the larger contact pressure (of 10 to 10 g/pin, for example) is maintained between the external leads 102 and the contact terminals 40 by this reaction, thereby enabling semiconductor devices 100 to be inspected. Inspection tests are successively made with respect to semiconductor devices 100 successively mounted on the socket frame 20 provided in the measuring unit 220 of the semiconductor inspection system 200.
In the conventional semiconductor inspection apparatus thus arranged, the contact terminals provided on the socket frame are formed of metallic members having an elasticity while the surfaces of the external leads of tested semiconductor devices are processed by solder dipping or solder plating for the purpose of facilitating mounting on a printed circuit board. If such contact terminals and external lead surfaces are repeatedly brought into contact and pressed against each other in a temperature environment of -50.degree. to +125.degree. C. solder 103 on the mounted surfaces 104 is transferred to the contact surfaces 44 of the contact terminals 40 and is attached to and deposited on these surfaces. This problem will be described in more detail. U-shaped curved portions 42 are formed in the contact terminals 40 to make the same elastic. Therefore, the contact surfaces 44 of the contact terminals move in the direction of arrow A shown in FIG. 28 in such a manner as to scrape off solder 103 from the mounted surfaces 104 of the external leads 102 each time the mounted surfaces 104 are brought into contact with and pressed against the contact surfaces 44. Solder 103 is attached to and deposited on the contact surfaces 44 if such a movement is repeated. The solder deposited in this manner is oxidized, causing electrical contact failure and is reversely transferred to the external leads to cause a short circuit between adjacent external leads. Also, the solder may fall upon being separated and cause electrical and mechanical failures or deform the mounted surfaces 104 of the external leads, which must have a certain degree of flatness. It is therefore necessary to frequently clean or change the contact terminals.
Also, semiconductor devices having external leads arranged with a small pitch (of 0.5 mm or smaller) have been developed. It is difficult to provide contact terminals on the socket frame with such a small pitch, and the structure of the conventional inspection apparatus is difficult to adapt to inspect semiconductor devices having finer external leads.